Bay was scratched from the lineup against the Nationals because of discomfort in his rib cage during batting practice, and the team acknowledged there was a chance he would start the season on the disabled list.

Mets general manager Sandy Alderson said it appears to be a strained left rib cage. Bay was replaced in Tuesday’s lineup by Lucas Duda.

Bay planned to return to the Mets’ spring training base in Port St. Lucie to be checked Tuesday afternoon. The Mets have until 11 a.m. Thursday to make a roster move if he needs to go on the DL.

“It’s a possibility, of course, this late in spring, but we’ll wait and see what happens and keep following it the next couple days until we get a feel for what it actually is and how it’s progressing,” Alderson said. “We’ll probably have a move or two we won’t make until the very end.”

On Saturday, Bay missed New York’s Grapefruit League game against the Atlanta Braves with a stiff back.

Alderson said the team did not think the rib cage and back ailments were related.

“But he hasn’t been examined yet by an orthopedist,” Alderson said.

Bay said on Saturday it was just “stiffness, soreness.”

The three-time All-Star was expected to provide a big offensive spark when he signed a four-year, $66 million contract before the 2010 season, but missed the final two months with a concussion.

“I’m Back to 100 percent, been that way for a couple months now,” Bay told WFAN’s Boomer & Carton in December. “I’ve been off for awhile, so I’m kind of itching to get back out there.”

He hit .259 in 2010 with just six home runs and 47 RBIs. It was the first time since 2003 — when Bay played just 30 games — that he didn’t hit at least 21 home runs.

The club is waiting on more test results due back by the end of the week before the severity can be determined.

“It does appear there are stomach and colon issues that will keep him out for a while, and we don’t know the extent of either of those, but we do think it will keep him out for a while based on the medication he’ll have to take,” Alderson said.

Paulino is suspended through the first eight games of the season anyway as he finishes out a 50-game suspension from last year, related to use of performance-enhancing drugs. Mike Nickeas will serve as Josh Thole’s backup until Paulino returns.

How much of a concern is Bay’s injury? Let us know in the comments below…

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